Until - ambiguity

Question

Hello I have big ambiguity in using this word: UNTIL. Does it include the thing after word UNTIL or it means that thing is not included?

Here are two examples:

A.

The TV Show was good until 3rd serie. - Does it mean 3rd serie was the last good serie or the last good serie was 2nd and 3rd was already bad?

B.

There were no problems until the 5th car/customer. - Does it mean 5th car/customer was already problematic? Or that 5th car/customer was OKAY but after 5th there were problems?

I hope you can see my problem, in this. If I should not use word UNTIL what should I use to be more clear? Can somebody give me proper answer? Thank you.

Answer 1

Usually it means that thing is not included. For example if I say "I have work until 5" it means I work until it is 5:00, and then I stop working at 5:00. I do not work the 5:00 hour.

Answer 2

In most contexts, until X would be understood as meaning up to, but not including, X (alternatively, until X starts, not until X finishes), so in #A above the speaker probably didn't think Series 3 was any good, and in #B the 5th car probably was problematic. But as you imply, there is the potential for ambiguity - for example, given the assertion He's at work until Friday, not everyone would agree on whether this implied he either would or wouldn't be at work on Friday.